Restructuring (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 26, 2014 USD ($)	Sep. 30, 2016 USD ($) employee	Sep. 25, 2015 USD ($)	Sep. 26, 2014 USD ($) employee
Restructuring Reserve [Roll Forward]
Restructuring charges		$ (1,233)	$ 80	$ (2,403)
2016 Restructuring Plan [Member]
Restructuring Reserve [Roll Forward]
Restructuring charges		(1,294)
Cash payments		(1,233)
Non-cash charges		(61)
Restructuring reserve, ending balance		0
Restructuring Charges [Member]
Restructuring Reserve [Roll Forward]
Restructuring charges		(1,300)		$ (3,300)
2014 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee				50
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		$ 0	146
Restructuring charges			(39)	$ (3,301)
Cash payments			(10)	(3,164)
Non-cash charges			(97)	(9)
Restructuring reserve, ending balance	$ 146		$ 0	$ 146
2013 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee		30
2013 Restructuring Program [Member]
Restructuring Reserve [Roll Forward]
Non-cash charges	$ (700)